Dog Cow, thanks for the reply.

I'm not sure that copy protection is the culprit here. Although I own the original game from many years ago, I am using a disk image obtained from another source with the emulator since my original disk cannot be read by my host pc's external USB floppy drive. And the game is getting past the point where it asks for the master disk.

Once the locked master has been processed, the program prompts for the scenario disk again. If I remember correctly, on a physical Mac, the master would be physically ejected at that point so that the scenario could be re-inserted. But the game fails because the emulator sees the scenario image as still in use, and refuses to allow it to be mounted again. The application never sees the scenario disk being re-inserted, and never proceeds past that modal dialog.

My guess would be that there may be a bug in the disk mounting/dismounting routine in the emulator.

Again, Dog Cow, thanks for your help. I'm still hoping that someone out might know or be able to suggest a workaround.